Electrical heating element



Jami 22, 19297 1,699,737

EEEEEEEEEEEEEEEEEEEEEE NT Filed June 3'7, 1927 2 Sheets-Sheet 1 JNVENTOR W/W/amWes/ey hlcks Y I m 7 4 A TTORNE YS Jan. 22, 1929. 1,699,737

W. W. HICKS ELECTRI CAL HEATING ELEMENT Filed June 27, 1927 2 Sheets-Sheet 2 P I E- IE...

IN VENTOR yd/fem es/e Hicks A TTORNE YS Patented Jan. 22, 1929.

NT OFFICE.

WILLIAM WESLEY HICKS, 01 SAN FRANCISCO, CALIFORNIA.

ELECTRICAL HEATING '1;

Application filed June 27,

.This invention relates generally toelec: trical heating elements Such as are incorporated in. various electrical heating ap- ,pllances.

Many forms of electrical heating appliances are constructed so that the resistance conductors are entirely concealed from view. For example in the case of electrical hot plates employed for cooking purposes, it is customary to utilize an imperforate metal plate having insulated resistance conductors in close thermal contact with the lower face of the plate. When the controlling switch for such an appliance is turned on, the operator has no positive way of determining immediately whether ,or not the resistance conductors are being energized, since considerable time is necessary for the entire plate to be perceptively heated. Furthermore unless complicated external signaling means is employed, an operator has no means for visually-determining Whether or not a closed appliance of this type is being energized even though the plate has attained a considerable temperature. In testing electrical heatingapphanceshaving heating ele ments of this kind, electricians waste considerable time in determining the presence of an'open circuit due either to a burned out resistance element or to an open fuse.

It is an object of this invention to incorporate means in a heating element of the closed type for positively indicating to the operator whether or not the-resistance conductors are being energized.

\ It is a further object of this invention to incorporate means forminga minor portion of the heat transferring surface of a heat- I ing element, for providing a visual indication of the temperature condition of the heating conductor It is a further object 'of this invention to utilize fused quartz .for the purposejof transmitting a light indication from a resistance conductor which is concealed within opaque heat conducting material.

Further objects of this invention will appear from -the following description in which I have set forth the preferred embodiment of m invention. It is" to be un derstood that. he appended claims are to be accorded a range of equivalents consist- Q ent with the state of the prior art.

Referring to the drawing:

Figure l is a top plan view of a hot plate' I the line '22 of Fig. 1. j

1927. Serial no. 2o1,s2o.

incorporating the principles of this invention.

Fig. 2 1s a cross sectional View taken along Fig. 3 is a bottom plan view. of the hot plateshown in Fig.1, ,the bottom casingbeing removed to show the positioning of the resistance conductors within grooves provided on the lower face of the heat conducting members J F ig. 4 is a cross sectional detail illustrating a modified form of signaling means for indicating the temperature condition of a resistance conductor..

Fig. 5 is a view similar to Fig. 4 showing a further modified form of signaling means.

The invention may be 'outlinedbriefly as comprising. a heat conducting member of opaque material, such as ordinary cast iron, the outer face of the member forming a heating transferring surface, and the inner face beiifgin heat absorbing relationship with a resistance conductor. Extending through the heat. conducting member there is a. piece of light transmitting material capable of withstanding a relatively high temperature, as for example a piece of fused quartz The inner end of this piece of quartz is exposed to the light glow of the resistance conductor while the outer end preferably terminates contiguous with the outer face Where it maybe viewed by the operator. p r

Referring now to the specific embodiment of the invention illustrated in the drawing, there is shown an electrical hot plate comprising a relatively flat member 10 of opaque heat conducting materiahsuch as cast iron or other-suitable metal. In thermal contact with the lower, face of,the member 10, are the coiled resistance conductors 11 which for convenience may be divided "into two resistance elements, one serving to heat the center portion of the plate and the other serving to heat the outer portion. In order to secure efficientrtransfer of heat from the conductors llto the member 10, these conductors are preferably disposed between ribs 12 formed upon thelower face of member 10 and integral therewith. F or example these ribs may be so disposed upon the plate so as to form a spiral groove 13. When themember 10 is made of metal or electrical conductive material, the resistance conductors 11 are insulated by suitable means such as refractory beads or tubes 14 which are sufficient in diameter to substantially fill the groove 13. The refractory tubes and the resistance conductors are retained in operative position between the ribs 12 as by means of unvitrified refractory cement 16. As is usualwith hot plates of this kind, the member 10 is retained in operative position upon an electrical range top 17 or other suitable support, and has its lower face enclosed by suitable means such as a metal pan 18. Terminal connectors 19" mounted upon this pan serve as a means for making electrical connections to the terminal wires of the resistance conductors 11.

In a hot plate such as described above it is impossible for an operator to actually see the resistance conductors in order to determine if they'are at a glowing temperature. In this invention however such a temperature condition is indicated to the operator by means of one or more members 21 of light transmitting material which extend thru the heat conducting member 10. The material of which these light transmitting members are constructed must be such that they will withstand the relatively high tempera-' tures and sudden temperature changes. to which the plate is normally subjected. For example I may employ a special form of glass capable of withstanding a high temperature, but -'the material which I prefer to employ is transparent fused quartz. Not only will fused quartz withstand high temperatures and sudden temperature changes without breakage, but it has the peculiar property of transmitting light-in the direction of its axis, eyen tho the axis may be bent at an acute" angle. A number of different expedients may lie employed for exposing the inner end of member 21'to the adja-- cent portion of one of the resistance conductors. In Figs. 2 and 3 I have shown that portionof the resistance "conductor adjacent the inner end of member 21 as being insulated by means of a special tube 22 of light transmitting material such as fused quart-z. For retaining the member 21 in position, it

may be tapered upwardly and seated within a conical aperture 23 with the inner end. ofthe member 21 in abutment with the periphcry of the fused quartz tube .22. v

' As a modification of the structures shown in Figs- 2 and 3, I may construct the quartz tube 22 and the member 21 integral as shown in Fig. 4. Thus in this instance the quartz tube 122 which serves to insulate the resistance conductor from the walls of the metal heat conducting member 10, is providedwith an integral projecting member 121 which extends thru an aperture 26 in the heat conducting member 10.

A further modification is shown in Fig. 5 in which the light transmitting member 221 is formed to provide a lens for magnifying a light indication. In this instance the refractory tube 27 covering that portion of the resistance conductor adjacent to the member 221 is provided with an aperture 28 for exposing the lower end of member 221 to the light glow from the resistance conductor. The upper and lower ends of member 221 are provided with curved convex surfaces 29 and 31 so that a maximum amount of light glow will be transmitted to member 221 and diffused from the upper end thereof.

As shown in Figs. 1 and 3, a plurality of light indicating means may be employed with one heating appliance and where the heating appliance employs two separate resistance elements, as with the appliance described abovc, I preferably utilize an in? dicating means for each element. Thus as shown in Figs. 1 and 3 one of the light transmitting members 21 is operatively positioned with respect to the outer resistance conductor while the other is operatively positioned with respect to the inner conductor.

lVhen one or more of the resistance conductors are being energized, the reddish light glow transmitted from the radiant resistance conductor will be transmitted thru the fused quartz member and will at once be visible to an operator. Intesting the plate for a burned out resistance element,

or to determine if a fuse'is open, the electrician can at once see if one or both of the elements. are being energized without waiting for the plate to become heated, or if one of the heating elements has become .open circuited, he can determine which element is still operable. As the upper end of the quartz members terminate contiguous, with the upper face of the heat conducting member 10, or what may be termed the heat transferring surface, normal operation of the device is not impaired and all of the advantages of a hot plate of the closed type are still retained.

I claim:

1. In an electrical heating appliance, a

resistance conductor adapted to be healed to a glowing temperature, metallic means arranged to'substantially conceal said conductor, said metallic means including an imperforate heat transferring surface of substantial area, and means for signalling the temperature condition of the conductor to an observer; comprising a member of light transmitting material, one end of said member terminating adjacent a portion of said conductor, and the other end thereof extending thru said metallic means and forming a portion of said heat transferring surface.

2. In an electrical heating element, a 'resistance conductor adapted to be heated to a glowing temperature, metallic means adapted to substantially conceal said conductor, said metallic means including an imperforate heat transferring surface of substantial area, and means for signalling the temperature condition of the conductor to an observer comprising a member made of fused quartz, one portion of said member terminating adjacent a portion of said conductor, and another portion of the member extending 7 thru said metallic means and forming a minor portion of the heat transferring surface.

3. An electrical hot plate of the closed type comprising a relatively flat member of heat conducting material, a resistance conductor in heat transmitting relationship with the lower face of said membcr,'the upper face of said member forming a heat transferrlng surface of substantial area, and a plug of fused quartz-positioned in said member, the inner portion of said plug being exposed to a portion of the conductor, and the outer portion of said plug having a surface contiguous with said heat transfer-ring surface.

4. An electrical hot plate of the closed top type comprising a relatively flat opaque member of heat conducting-material, a resistance conductor in heat transmitting relationship with the lower face of said member, the upper face of said member forming a substantially planar heat transferring surface of substantial area for applying heat to the bottom of a cooking utensil, and a plug of light transmitting material inserted in said member, the inner portion of said plug being exposed to a portion of the conductor, and t-heOuter portion of said plug having a surface continuing the continuity of said heat transferring surface.

In testimony whereof, I have hereunto set my hand.

WILLIAM WESLEY HICKS. 

